Construction of hierarchical porous and polydopamine/salicylaldoxime functionalized zeolitic imidazolate framework-8 via controlled etching for uranium adsorption†

Efficient uranium extraction from seawater is critical for the development of the nuclear industry. Herein, a polydopamine/salicylaldoxime decorated hierarchical zeolitic imidazolate framework-8 (H-PDA/SA-ZIF-8) is constructed by using a controlled etching process. Benefiting from the combination of PDA/SA and the zeolitic imidazolate framework-8 (ZIF-8), as well as a controlled etching process, the H-PDA/SA-ZIF-8 possesses multiaffinity sites, excellent specific surface area (1234.92 m² g⁻¹), and a hierarchical pore structure. The H-PDA/SA-ZIF-8 exhibits excellent adsorption capacity (Q_m = 869.6 mg g⁻¹), selectivity, and reusability in uranium adsorption. The adsorption process of H-PDA/SA-ZIF-8 fits very well with the Langmuir isotherm model and pseudo-second-order models, and the adsorption process equilibrates within 20 min (C₀ = 20 mg L⁻¹). Furthermore, the H-PDA/SA-ZIF-8 shows remarkable antibacterial ability. Impressively, the adsorption capacity of H-PDA/SA-ZIF-8 to uranium in natural seawater reaches 6.9 mg g⁻¹ after circulation for 15 days. Therefore, the H-PDA/SA-ZIF-8 is a promising and fascinating material for uranium extraction from natural seawater.